1. Field of the Invention
This invention relates to an attachment to an envelope feed machine used to feed envelopes continuously to a printer, and more particularly to an envelope feeder for driving envelopes one by one so as to feed them to a temporary storage station which is located just under an air sucker in a stream feeder type printer.
2. Description of the Prior Art
An envelope has folded, overlapped and pasted portions, i.e., it does not have a uniform thickness. Therefore, when a plurality of envelopes are stacked before they have been fed to a printing position, they are inclined. Accordingly, only several hundred envelopes at most can be stacked directly on a paper feeder for a printer, and, moreover, it is impossible to expect that these envelopes be kept stable on the paper feeder. Interrupting a printing operation every time several hundred envelopes have finished being printed causes the operation efficiency to decrease to an extremely low level. In order to prevent this inconvenience, such a system is generally employed that a special envelope feeder is connected to the paper feeder for a printer so as to store a suitable number of envelopes successively in piled state just under an air sucker for the paper feeder.
There is U.S. Pat. No. 4,369,959 disclosing such a type of envelope feeder which is roughly constructed as follows. A plurality of envelopes are piled in inclined state in a stack formed of a frame, and the piled envelopes are stripped one by one from the bottom of the stack and sent out by a diagonal conveyor. The envelopes are then inverted by an inversion conveyor which contacts the diagonal conveyor, and thereafter transferred in successively overlapped state by a horizontal transfer conveyor. The downstream end of the transfer conveyor is joined directly to the portion of a printer which is just under an air sucker of a paper feeder for the printer. The envelopes transferred successively in overlapped state are then piled up in several layers in a bottom layer-lifting manner on the downstream end portion of the transfer conveyor and stored in the same position temporarily to stand by ready to be picked up by the air sucker.
In order to pile up envelopes in a bottom layer-lifting PG,5 manner in a position just under the air sucker, the purpose is not met if the envelopes which have been sent thereto in mutually overlapped state along the surface of the transfer conveyor are merely forwarded as they are. It is necessary to drive the overlapped envelopes one by one toward a stopper provided at the front side of the transfer conveyor, and pile them up with the front ends of the envelopes aligned by this stopper.
It is a feeder that is added to an envelope feed apparatus for this purpose. The techniques relative to the feeder include, for example, those disclosed in Japanese Utility Model Laid-Open No. 78842/1983. These techniques are directed to an auxiliary transfer structure in which a holding roller is connected rotatably to the lower end portion of a support arm extending above a transfer conveyor, support shafts being provided so as to project from the outer side of the support shaft and the outer circumferential portion of the holding roller, respectively, the support shaft for the support arm being engaged with a horizontally-elongated guide bore made in the rear portion of a drive plate, the support shaft for the holding roller being engaged with a vertically-elongated bore made in the front portion of the drive plate.
However, since two support shafts are engaged with horizontally- and vertically-elongated guide bores, respectively, in this prior art transfer structure, the actions of the parts are not smoothly made, and the feed power is small, the reliability of the operation being low.
In order that the envelopes can be printed with a specially high efficiency, a stream feeder type printer having a high printing rate or a high feed rate is used. In such a printer, the rear end of each envelope is dealt with by an air sucker, and the envelopes are arrayed in a scalelike configuration, i.e., in continuously-overlapped state on a feeder board and fed to a printer body.
In order to prepare envelopes for the purpose of being printed properly by such a stream feeder printer, it is necessary that the largest possible number of envelopes be piled up in very good order and in a reliable manner in a storage station just under the air sucker. Accordingly, it is also necessary, of course, that a feeder is moved smoothly and has a large feed power. If an erroneous operation, in which the feeder runs on an envelope which is being piled on another, occurs, the performance of the stream feeder type printer cannot be effectively utilized, so that such an erroneous operation is in no case allowed.